The present invention relates to a method and apparatus for endoluminally deploying a graft across an aneurysm and, more particularly, to a catheterization method and apparatus for forming an endoluminal bifurcated graft, such as may be placed across an aortic aneurysm and any associated common iliac aneurysms.
Aortic aneurysms represent a significant medical problem for the general population. Aneurysms within the aorta presently affect between two and seven percent of the general population and the rate of incidence appears to be increasing. This form of atherosclerotic vascular disease (hardening of the arteries) is characterized by a degeneration in the arterial wall in which the wall weakens and balloons outward by thinning. An abdominal aortic aneurysm is a dilatation of the main artery of the body. Until the affected artery is removed or bypassed, a patient with an abdominal aortic aneurysm (xe2x80x9cAAAxe2x80x9d) must live with the threat of aortic aneurysm rupture and death. See Brody, J. E., xe2x80x9cAneurysm: A Potential Killer Lurking in the Aorta,xe2x80x9d The New York Times, Apr. 13, 1994, at C14.
One known clinical approach for patients with an abdominal aortic aneurysm is a surgical repair procedure. This is an extensive operation involving transperitoneal or retroperitoneal dissection of the aorta and replacement of the aneurysm with an artificial artery known as a prosthetic graft. This procedure requires a significant abdominal incision extending from the lower border of the breast bone down to the pubic bone to expose the abdominal aorta and the aneurysm so that the graft can be directly implanted. The operation requires a general anesthesia with a breathing tube, extensive intensive care unit monitoring in the immediate postoperative period, along with blood transfusions and stomach and bladder tubes. All of this imposes stress on the cardiovascular system. Also associated with this procedure are well recognized morbidity (15%) and mortality (2-7%) rates. See Ernst, C. B. xe2x80x9cAbdominal Aortic Aneurysms,xe2x80x9d New England J. Med., Vol. 328:1167-1172 (Apr. 22, 1993).
Today, there is the potential for a significantly less invasive clinical approach to aneurysm repair known as endovascular grafting. Parodi et al. provide one of the first clinical descriptions of this therapy. Parodi, J. C., et al., xe2x80x9cTransfemoral Intraluminal Graft Implantation for Abdominal Aortic Aneurysms,xe2x80x9d 5 Annals of Vascular Surgery 491 (1991). Endovascular grafting involves the transluminal placement of a prosthetic arterial graft in the endoluminal position (within the lumen of the artery). By this method, the graft is attached to the internal surface of an arterial wall by means of attachment devices (expandable stents), one above the aneurysm and a second stent below the aneurysm.
Stents are devices that permit fixation of a graft to the internal surface of an arterial wall without sewing. Expansion of radially expandable stents is conventionally accomplished by dilating a balloon at the distal end of a balloon-catheter. In U.S. Pat. No. 4,776,337, Palmaz describes a balloon-expandable stent which has received the greatest experimental and clinical application for endovascular treatments. Also known are self expanding stents, such as described in U.S. Pat. No. 4,655,771 to Wallsten. These patents are hereby incorporated in their entireties, by reference.
Attachment of the stents above and below the aneurysm is a conceptually straightforward procedure when the aortic aneurysm is limited to the abdominal aorta and there are significant portions of normal tissue above and below the aneurysm (see FIG. 1). Unfortunately, 40-60% of aneurysms do not have suitable neck portions of normal tissue at the caudal portion (farthest from the head) of the aorta. Also, the severe tortuosity of the iliac arteries and the marked angulation of the aortoiliac junction compound the difficulty of fixing the stent in the caudal portion of the aorta. This situation is only exacerbated by the tendency of the abdominal aortic artery to elongate caudally during aneurysm formation. For want of sufficient normal aortic tissue to suitably attach a prosthetic graft at the caudal end of an aneurysm, or because of extension of the aneurysmal sac into the iliac arteries, bifurcated grafts have been developed that comprise a single body terminating with two limbs.
As a therapy to bypass an abdominal aortic aneurysm as well as any associated common iliac aneurysms, endoluminal deployment of a conventional bifurcated graft has presented significant issues to clinical operators in the field, primarily with respect to the positioning of one of the limbs of the graft in the contralateral iliac artery. The contralateral iliac artery is the artery that the conventional endoluminal bifurcated graft is not being advanced through. This procedure requires that both limbs of the graft be inserted into one branch of the femoral arterial system before being drawn or pulled over to the contralateral branch. This is to ensure that the graft is suitably positioned within the aorta and each of the right and left common iliac arteries. Even when tightly packaged, the bifurcated graft is a bulky device to advance through an often narrow single iliac artery.
The process of pulling or drawing one limb of the graft to the contralateral artery is time consuming and increases the risk of procedural complications, such as twisting and kinking of the graft-limb and injury to the vessel wall which can result in micro-embolization. As one limb of the graft is pulled across the frequently tortuous and twisted iliac artery anatomy, the graft may twist or kink. Any graft twist or kink may reduce or entirely cut-off blood flow to the arterial tree downstream thereof.
The procedure of drawing one limb of the prosthetic graft from one branch of the arterial system to the contralateral branch requires significant and skillful wire catheter manipulation within the aneurysmal cavity. See, for example, Chuter T. A. M., et al., xe2x80x9cTransfemoral Endovascular Aortic Graft Placement,xe2x80x9d J. of Vascular Surgery 18:185-197, at 188-190 (August, 1993). This procedure may result in micro-embolization of clots which are known to form within aneurysmal sacs. If these clots are disturbed or dislodged from the aortic aneurysm, they may break up into small fragments and flow downstream to other arteries. The excessive wire manipulation may also induce xe2x80x9cchurningxe2x80x9d within the aneurysmal cavity which can cause proximal reflux or retrograde flow of thrombotic or embolic material into the arteries that supply circulation to the kidneys, intestines and the liver.
Accordingly, there exists a need for a method for safely and effectively bypassing an aneurysm, such as an abdominal aortic aneurysm, located at or extending into a bifurcation in the vasculature, such as the common iliac arteries. There also exists a need for an attachment device that permits the collateral deployment of stents as mirror image pairs, as well as an apparatus for deploying such an attachment device.
These and other needs are addressed, according to one aspect of the invention, by a method of endoluminally bypassing blood flow through an aneurysm. The method comprises the steps of advancing a graftstent complex through each branch of the branched blood vessel, aligning the cephalic stents of each of the graftstent complexes relative to each other in a common vessel above the aneurysm, and deploying each of the aligned cephalic stents in the common vessel. When the aneurysm is in the aortic artery, the graftstent complexes are advanced through the femoral and iliac arterial system and the cephalic stents are aligned in a common region of normal aortic tissue above the aneurysm. The alignment step may further comprise rotationally orienting the stents so that an alignment surface on each stent engages the other stent when the stents are deployed. Of course, the method may be performed in passageways other than those that form the arterial system, and may be performed by advancing the graftstent complex from a common passageway to a branched passageway. When the inventive method is performed in the vascular system, the deployed vascular stents are preferably expanded in a non-circular configuration, for example, in a generally xe2x80x9cDxe2x80x9d shaped configuration, and may be expanded simultaneously. The deployed stents preferably hemostatically seal the graftstent complexes to the common vessel wall and to each other so that blood is excluded from the aneurysmal cavity.
The invention also provides an apparatus for rotationally aligning a pair of indwelling stents mounted on separate catheter shafts. The shafts rotatably support the indwelling stents. The apparatus includes an indicating means on a proximal portion of each of the shafts for indicating the relative rotational orientation of the stents. Rotation of the proximal portion of the shafts provides a corresponding rotation of the stents, so that the relative rotational orientation of the indwelling stents is indicated by the proximal indicating means. In one embodiment, the indicating means comprises a marker on the proximal end of each of the shafts.
The invention also provides an apparatus that radially expands a vascular stent into a non-circular configuration. The apparatus comprises a member which is movably mounted with respect to a catheter, a deployment wire connected to the member for axially moving the member with respect to the catheter, and a plurality of wings which partially surround the member to form a support surface for the stent. The apparatus expands the stent into a non-circular configuration through a connection of a plurality of first and second arms which are of different lengths. Each of the wings is pivotally connected to a rigid portion on the catheter by one of the first and second arms so that the wings connected to the first arms displace radially outwardly more than the wings connected to the second arms when the movable member is moved axially by the deployment wire. This apparatus may also be used for collaterally deploying a pair of stents within a common body lumen.
The invention also provides in combination with an expandable prosthesis an apparatus for deploying the expandable prosthesis with a non-circular cross-section at a site within a body lumen. The apparatus includes a support for supporting the expandable prosthesis while being delivered to the site within the body lumen, and a radially displaceable mechanical linkage connected to the support. The linkage expands the prosthesis to a non-circular cross-section when displaced radially outward and is adapted to deploy the expandable prosthesis when radially displaced. The linkage permits continuous fluid flow within the body lumen while the expandable prosthesis is being deployed.
According to another aspect of the present invention, there is provided an expanded vascular stent which has a non-circular cross-section. The vascular stent may be of the self-expanding variety, and preferably has a generally xe2x80x9cDxe2x80x9d shaped configuration. In the preferred embodiment, the xe2x80x9cDxe2x80x9d shaped stent has a curved edge and an alignment edge. The curved edge engages a body lumen when expanded, whereas the alignment edge engages a collaterally expanded vascular stent. A segment of graft material having at least one end cut on a bias is attached to the stent so that the graft material extends substantially between the proximal and distal ends of the stent along the alignment edge, yet only partially along the curved edge. This advantageously assists in hemostatically sealing the bypassed aneurysm from the patient""s blood flow.
According to yet another aspect of the present invention, a graftstent complex for hemostatically bypassing an aneurysm is provided. The graftstent complex comprises a segment of graft material, a balloon-expandable stent, and a self-expanding stent. The segment of graft material is attached at one end to the balloon-expandable stent and at another end to the self-expanding stent. The graftstent complex may have the segment of graft material cut on a bias, as noted above.
These and other objects, features and advantages of the present invention will be readily apparent from the following detailed description of the invention taken in conjunction with the accompanying drawings.